1. Field of the Invention
The invention concerns a continuously conductive unipolar cannula for anesthesia.
2. Description of the Relate Art
A continuously conductive unipolar cannula for anesthesia produced by the company Pajunk GmbH, D-78187, Geisingen, Germany is known, which has an electrically conductive cannula tube, the tube having an electrically insulated outer covering which extends from the proximal body part out to the distal tip of the cannula tube and leaves exposed the distal tip in its distal end area. In the area of the proximal body part, the cannula tube is electrically contacted with a connector, which can be connected to an electro-stimulation device via a socket or jack. The distal tip of the cannula tube is either provided with a facet cut or is designed as a so-called Sprotte tip as disclosed in DE 30 20 926 C2.
In this known unipolar cannula, the connector for electro-stimulation and an injection hose for the anesthetic are provided introduced axially parallel next to each other in the proximal end face of the body part of the cannula tube. The unipolar cannula can be placed exactly in the nerve sheath with its distal tip using electro-stimulation, in order to then be able to apply the anesthetic via the feed hose precisely on the nerve.
In the continuously conductive anesthesia, a catheter is placed in the nerve sheath, in order to be able to introduce anesthetic over a longer period of time. In order to introduce a catheter using the known unipolar cannula, a plastic introducer cannula is pulled over the cannula tube, which is placed under electro-stimulation by means of the unipolar cannula. As soon as the plastic introducer cannula is in place, the unipolar cannula is withdrawn and then the catheter can be introduced through the plastic introduction cannula.
It is further known from DE 36 43 235 C1 and DE 37 12 869 C2, to design a cannula with Sprotte-tip, such that through this cannula itself a catheter can be introduced in place. For this, a ramp or guide is formed in the inside of the distal tip of the cannula tube, which leads to a side outlet opening. A catheter introduced proximally in the cannula tube is led out of the cannula tube via this ramp through the side outlet opening. This cannula is suitable for the placement of a catheter without a supplemental introducer cannula. An electro-stimulation is, however, not possible with this known cannula. Accordingly, this cannula is not provided with an electrical connection for electro-stimulation.